More importantly after mentioning charting and stuff on the Dia mailing list James DuPont pointed me at some peers of the Graphviz project and even a Graph/Chart XML schema.
VCG (Visualiser of Compiler Graphs) - offers auto-layout and folding and stuff, very very cool but I haven't had a chance to play yet.
Graphotron 'Graphotron is a simple XML language for drawing graphs with XPath' apparently.
as a side note - I have managed to get a simple Traffic Analysis Graph working with real web logs at work. Its not very pretty but I am certain that it will be very helpful - even more so if I combined it and a couple of other charts into a database backend to provide interrogation tools.